.netcore使用MimeKit发送邮件

以163邮箱为例，借助MimeKit

nuget安装：MimeKit类库，源码地址：https://github.com/jstedfast/MimeKit

发送方法如下：

#region 邮件发送
        /// <summary>
        /// 邮件发送
        /// </summary>
        /// <param name="sendName">发送者名称</param>
        /// <param name="sendAccountName">发送者账号</param>
        /// <param name="smtpHost">发送者服务器地址：例如：smtp.163.com</param>
        /// <param name="smtpPort">服务器端口号：例如：25</param>
        /// <param name="authenticatePassword">发送者登录邮箱账号的客户端授权码</param>
        /// <param name="receiverAccountNameList">接收者账号</param>
        /// <param name="mailSubject">邮件主题</param>
        /// <param name="sendHtml">文本html(与sendText参数互斥，传此值则 sendText传null)</param>
        /// <param name="sendText">纯文本(与sendHtml参数互斥，传此值则 sendHtml传null)</param>
        /// <param name="accessoryList">邮件的附件</param>
        public static void SendMail(string sendName, string sendAccountName, string smtpHost, int smtpPort, string authenticatePassword, List<string> receiverAccountNameList, string mailSubject, string sendHtml, string sendText, List<MimeKit.MimePart> accessoryList = null)
        {
            var message = new MimeKit.MimeMessage();
            message.From.Add(new MimeKit.MailboxAddress(sendName, sendAccountName));
            var mailboxAddressList = new List<MailboxAddress>();
            receiverAccountNameList.ForEach(f =>
            {

                mailboxAddressList.Add(new MailboxAddress(f));
            });
            message.To.AddRange(mailboxAddressList);

            message.Subject = mailSubject;

            var alternative = new MimeKit.Multipart("alternative");
            if (!string.IsNullOrWhiteSpace(sendText))
            {
                alternative.Add(new MimeKit.TextPart("plain")
                {
                    Text = sendText
                });
            }

            if (!string.IsNullOrWhiteSpace(sendHtml))
            {
                alternative.Add(new MimeKit.TextPart("html")
                {
                    Text = sendHtml
                });
            }
            var multipart = new MimeKit.Multipart("mixed");
            multipart.Add(alternative);
            if (accessoryList != null)
            {
                accessoryList?.ForEach(f =>
                {
                    multipart.Add(f);
                });

            }
            message.Body = multipart;
            using (var client = new MailKit.Net.Smtp.SmtpClient())
            {
                client.Connect(smtpHost, smtpPort, false);
                client.AuthenticationMechanisms.Remove("XOAUTH2");
                client.Authenticate(sendAccountName, authenticatePassword);
                client.Send(message);
                client.Disconnect(true);
            }
        }

        #endregion

使用方法：

SendMail("发送人名称", "xxxxxxx@163.com", "smtp.163.com", , "xxxxxxxxx授权码", new List<string> { { "xxxxxx@qq.com" } }, "邮件主题", @" <p>邮件文本</p> ", null, accessoryList: new List<MimePart>()
            {
                {
                    new MimeKit.MimePart("audio","mp4")
                    {
                        ContentObject = new MimeKit.ContentObject(File.OpenRead("C:\\Users\\lyj\\Desktop\\图片\\下载 (5).mp4"), MimeKit.ContentEncoding.Default),
                        ContentDisposition = new MimeKit.ContentDisposition(MimeKit.ContentDisposition.Attachment),
                        ContentTransferEncoding = MimeKit.ContentEncoding.Base64,
                        FileName = Path.GetFileName("C:\\Users\\lyj\\Desktop\\图片\\下载 (5).mp4")
                    }
              },
                {
                    new MimeKit.MimePart("audio","mp4")
                    {
                        ContentObject = new MimeKit.ContentObject(File.OpenRead("C:\\Users\\lyj\\Desktop\\图片\\下载 (3).mp4"), MimeKit.ContentEncoding.Default),
                        ContentDisposition = new MimeKit.ContentDisposition(MimeKit.ContentDisposition.Attachment),
                        ContentTransferEncoding = MimeKit.ContentEncoding.Base64,
                        FileName = Path.GetFileName("C:\\Users\\lyj\\Desktop\\图片\\下载 (3).mp4")
                    }
                },
                {
                    new MimeKit.MimePart("image","jpg")
                    {
                        ContentObject = new MimeKit.ContentObject(File.OpenRead("C:\\Users\\lyj\\Desktop\\图片\\11timg.jpg"), MimeKit.ContentEncoding.Default),
                        ContentDisposition = new MimeKit.ContentDisposition(MimeKit.ContentDisposition.Attachment),
                        ContentTransferEncoding = MimeKit.ContentEncoding.Base64,
                        FileName = Path.GetFileName("C:\\Users\\lyj\\Desktop\\图片\\11timg.jpg")
                    }
                }
        });

收录一些邮件服务地址对应的端口：https://blog.csdn.net/zdqdj1/article/details/48030023